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Abstract:

An LED unit includes a plate-shaped base; a light-emitting device placed
on a surface of the base and having one or more LED chips; and a cover
mounted to the base at a location above a front side of the
light-emitting device and having a function to transmit light emitted
from the light-emitting device. The base has on the surface thereof an
annular groove for receiving a seal therein, and the cover has on a
surface thereof directed to the base an annular protruding part, the
annular protruding part being inserted into the annular groove to seal
the base and the cover through the seal. A distance between the
protruding part and the groove in a width direction of the groove is
shorter in a section of the groove than the other sections of the groove.

Claims:

1. An LED unit, comprising: a plate-shaped base; a light-emitting device
placed on a surface of the base and having one or more LED chips; and a
cover mounted to the base at a location above a front side of the
light-emitting device and having a function to transmit light emitted
from the light-emitting device, wherein the base has on the surface
thereof an annular groove for receiving a seal therein, and the cover has
on a surface thereof directed to the base an annular protruding part, the
annular protruding part being inserted into the annular groove to seal
the base and the cover through the seal, and wherein a distance between
the protruding part and the groove in a width direction of the groove is
shorter in a section of the groove than the other sections of the groove.

2. The LED unit of claim 1, wherein the groove has a circular ring shape
and a protruding portion protruding inward of the groove, the protruding
portion being provided at the section of the groove, so that the distance
between the protruding part and the groove in the width direction of the
groove is shorter in the section of the groove than the other sections of
the groove.

3. A lighting fixture, comprising: an LED unit described in claim 1, and
a housing in which the LED unit is installed.

4. A lighting fixture, comprising: an LED unit described in claim 2, and
a housing in which the LED unit is installed.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to an LED unit and an lighting
fixture using the LED unit.

BACKGROUND OF THE INVENTION

[0002] Conventionally, a lighting fixture having an LED unit (LED lighting
fixture) has been proposed (for example, Japanese Patent Application
Publication Nos. 2003-59330 and 2008-258066 (JP2003-59330A and
JP2008-258066A)].

[0003] The LED lighting fixture disclosed in JP2003-59330A has an LED
module board 37 on which LED chips 36, etc. are mounted, as shown in FIG.
15. On the LED module board 37, a terminal block 24 having terminals 39
used for directly connecting feeder wires 38 to the LED module board 37
is provided. In the terminal block 24, release buttons 25 for releasing
the feeder wires 38 from the respective terminals 39 are provided.
Further, in the LED lighting fixture having the LED module board 37, the
LED chips 36, the LED module board 37, the terminal block 24 and the like
constitute an LED unit.

[0004] Further, the LED lighting fixture disclosed in JP2008-258066A is,
for example, a pendant light that is a lighting fixture suspended from a
ceiling. As shown in FIGS. 16A and 16B, this LED lighting fixture
includes an LED board 27 having LEDs 26 thereon, and a power circuit 28
for supplying electricity to the LED board 27. This LED lighting fixture
further includes a cylindrical LED casing 29 having a base for holding
the LED board 27, and a cylindrical power casing 30 for holding a power
circuit 28. The power casing 30 is separated from the LED casing 29 and
has a base. Further, the power casing 30 is placed above the LED casing
29.

[0005] In a bottom wall 30c of the power casing 30, there is a cord
passing hole 30d through which a power-side cord 32 electrically
connected to the power circuit 28 can pass. The distal end of the
power-side cord 32 is provided with a connection plug 32a. Further,
locking hooks 34 used for holding the LED casing 29 protrude from the
lower surface of the power casing 30. The locking hooks 34 are arranged
at regular intervals in a circumference direction.

[0006] An upper plate 29a is attached to the In the LED casing 29 to close
the space defined in the LED casing 29. The upper plate 29a has a cord
passing hole 29b through which an LED-side cord 33 electrically connected
to the LED board 27 passes. At the leading end of the LED-side cord 33, a
connection plug 33a that is removably connected to the connection plug
32a of the power-side cord 32 is provided. Further, in the upper plate
29a, locking holes 35 are formed correspondingly to the locking hooks 34
of the power casing 30 so that the locking hooks 34 can be engaged with
the respective locking holes 35. Accordingly, the LED lighting fixture
having the construction shown in FIGS. 16A and 168 can be assembled by
bringing the upper plate 29a of the LED casing 29 into surface contact
with the bottom wall 30c of the power casing 30. Further, in the LED
lighting fixture having the construction shown in FIGS. 16A and 168, the
LEDs 26, the LED board 27, the LED casing 29, the upper plate 29a, the
LED-side cord 33 and the connection plug 33a constitute an LED unit.

[0007] However, considering the LED unit is used in a variety of
environments, it is preferred that the LED unit be provided with a
sealing structure capable of preventing moisture or impurities from being
introduced into the LED unit. Here, although it is not related to an LED
unit, there has been proposed, as a structure for improving the
watertightness between a pair of housing bodies, a sealing structure that
is a packing formed by hardening a sealing material filled in a groove of
one of the pair of housing bodies with a space provided between the
sealing material and one side surface of the groove by using a jig (for
example, Japanese Patent Application Publication No. H11-340648
(JP11-340648A)). Another sealing structure that is formed by applying a
silicone resin having a lower hardness in a groove of one of a pair of
housing bodies and by applying another silicone resin having a higher
hardness on the silicone resin having the lower hardness and is used as a
seal between the pair of housing bodies has been proposed (for example,
Japanese Patent Application Publication No. H10-324360 (JP10-324360A)). A
further sealing structure that is formed by placing a separately produced
annular packing in an annular groove defined in a pair of housing bodies
engaged with each other has been proposed (for example, Japanese Patent
Application Publication No. 2010-252224 (JP2010-252224A)). Still another
sealing structure that is formed by placing spherical sealing materials
in a groove of one of a pair of housing bodies has been proposed (for
example, Japanese Patent Application Publication No. 2010-251616
(JP2010-251616A)).

[0008] However, in each of the sealing structures disclosed in
JP11-340648A and JP10-324360A, a liquid sealing material is used.
However, a long time is required to harden the sealing material after the
sealing material is applied, so that it is problematic in that the long
hardening time may reduce the productivity. Particularly, when the
hardening time of the sealing material is too long, the housing bodies
may not be appropriately sealed in desired locations due to unexpected
vibration or external force applied to the housing bodies during an
assembling process. Further, when the sealing material is being hardened,
the sealing material may be deformed or bubbles may be formed in the
sealing material so that close contact between the housing bodies that
are to be sealed by the sealing material may not be accomplished.
Further, in the sealing structure disclosed in JP2010-252224A in which
the annular packing is used to seal the housing bodies, a period of time
is required to place the annular packing in the groove of the housing
bodies, thereby resulting in a poor productivity. Further, when the
annular packing is not precisely placed at a predetermined location in
the groove of the housing body or the packing is placed in the groove in
a deformed state, desired watertightness of the packing may not be
accomplished. Further, in the sealing structure using the spherical
sealing materials disclosed in JP2010-251616A, it is necessary to place a
predetermined number of spherical sealing materials at predetermined
locations in the groove and when any one spherical sealing material is
not placed, desired watertightness may not be realized. Further, because
it is necessary to place the predetermined number of spherical sealing
materials in the groove without missing any one material, it is difficult
to automatically place the sealing materials using an automated machine
and work efficiency of manual assembly performed by a person is low, thus
deteriorating the productivity.

[0009] Particularly, the LED unit may emit light from a light-emitting
device through a lens provided in a cover. Further, when the sealing
structure disclosed in each of JP11-340648A, JP10-324360A, and
JP2010-251616A is used in an LED unit, the optical characteristics of the
LED unit may be largely influenced by a positional error of the cover.

SUMMARY OF THE INVENTION

[0010] In view of the above, the present invention provides an LED unit
and a lighting fixture using the LED unit, capable of realizing increased
watertightness and a high productivity.

[0011] In accordance with one aspect of the present invention, there is
provided an LED unit including a plate-shaped base; a light-emitting
device placed on a surface of the base and having one or more LED chips;
and a cover mounted to the base at a location above a front side of the
light-emitting device and having a function to transmit light emitted
from the light-emitting device, wherein the base has on the surface
thereof an annular groove for receiving a seal therein, and the cover has
on a surface thereof directed to the base an annular protruding part, the
annular protruding part being inserted into the annular groove to seal
the base and the cover through the seal, and wherein a distance between
the protruding part and the groove in a width direction of the groove is
shorter in a section of the groove than the other sections of the groove.

[0012] In the LED unit, the groove may have a circular ring shape and a
protruding portion protruding inward of the groove, the protruding
portion being provided at the section of the groove, so that the distance
between the protruding part and the groove in the width direction of the
groove is shorter in the section of the groove than the other sections of
the groove.

[0013] In accordance with another aspect of the present invention, there
is provided a lighting fixture, including: the LED unit described above
and a housing in which the LED unit is installed.

[0014] As described above, the LED unit of the present invention has an
increased watertightness and high productivity.

[0015] The lighting fixture of the present invention uses the LED unit
that has a high level of watertightness and productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other objects and features of the present invention
will become apparent from the following description of preferred
embodiments given in conjunction with the accompanying drawings, in
which:

[0017] FIG. 1 is an exploded perspective view of an LED unit in accordance
with an embodiment of the present invention;

[0018] FIG. 2 is a sectional view of the LED unit;

[0019] FIGS. 3A and 3B are views illustrating a main part of the LED unit,
in which FIG. 3A is a plan view and FIG. 3B is an enlarged plan view;

[0020] FIG. 4 is a view illustrating the LED unit;

[0021] FIGS. 5A and 5B are views illustrating main parts of the LED unit,
in which FIG. 5A is a bottom view of a cover and FIG. 5B is a bottom view
of a cover pressing member;

[0022] FIGS. 6A through 6C are views illustrating a process of assembling
the LED unit;

[0023] FIGS. 7A through 7C are views illustrating the process of
assembling the LED unit;

[0024] FIGS. 8A and 8B are views illustrating the process of assembling
the LED unit;

[0025]FIG. 9 is a sectional view of an LED lighting fixture having the
LED unit;

[0026]FIG. 10 is a sectional view of another LED lighting fixture having
the LED unit;

[0027] FIG. 11 is a sectional view of still another LED lighting fixture
having the LED unit;

[0028] FIG. 12 is a sectional view of still another LED lighting fixture
having the LED unit;

[0029] FIG. 13 is a sectional view of still another LED lighting fixture
having the LED unit;

[0030] FIG. 14 is a sectional view of still another LED lighting fixture
having the LED unit;

[0031]FIG. 15 is a perspective view of an LED module board used in a
conventional LED lighting fixture; and

[0032] FIGS. 16A and 16B are views illustrating another conventional LED
lighting fixture, in which FIG. 16A is a sectional view and FIG. 16B is a
perspective view.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Hereinafter, preferred embodiments of the present invention will be
described in detail with reference to the accompanying drawings which
form a part hereof.

First Embodiment

[0034] Hereinbelow, an LED unit 10 in accordance with a first embodiment
of the present invention will be described with reference to FIGS. 1
through 8B.

[0035] The LED unit 10 of this embodiment includes a plate-shaped base 1
(for example, a disc-shaped base) having a support block 1f on a first
surface thereof (an upper surface in FIG. 1), and a heat dissipating
sheet 9 that is made of a material having both high electrical insulation
property and high heat conductivity is placed on an upper surface 1fa of
the support block 1f. Further, the LED unit 10 is provided with a
light-emitting device 3 using one or more LED chips (not shown) placed on
a surface of the heat dissipating sheet 9 opposite to the support block
1f. The LED unit 10 further includes a holder 2 of tube shape, e.g., a
cylindrical shape having bottom wall, for holding the light-emitting
device 3 between the holder 2 and the base 1, and a cover 20 that is
disposed on a front surface (an upper side in FIG. 1) side of the
light-emitting device 3 and is mounted to the first surface of the base 1
and functions to transmit therethrough light emitted from the
light-emitting device 3.

[0036] Particularly, on the first surface of the base 1 of the LED unit
10, an annular groove 1t for receiving a seal 5 therein is formed. An
annular protruding part 20e extends from the cover 20 in a direction
toward the base 1 and is inserted into the groove 1t so that the seal 5
can seal both the base 1 and the cover 20 (see FIGS. 3A, 3B and 4). The
groove 1t further includes inward protrusions 1tb that are formed on an
outside circumferential surface of the groove 1t, for example, at
diametrically opposite locations, in which the distance between the
protruding part 20e and the groove 1t in a width direction of the groove
1t is shorter in a section of the groove 1t having the inward protrusions
1tb than the other sections of the groove 1t.

[0037] Further, the LED unit 10 includes a pair of power-feeding wires
(lead wires) 4 that are electrically connected to the light-emitting
device 3.

[0038] The base 1 used in the LED unit 10 of this embodiment is made of
aluminum by a die-casting process, with the support block 1f integrally
formed on the first surface of the base 1. Here, the base 1 may be made
of a material having higher thermal conductivity than that of resin
materials, for example, metal, such as copper or stainless steel, without
being limited to aluminum. Further, the support block 1f may be
integrated with the base 1 in a single piece as described above or may be
manufactured separately from the base 1.

[0039] At the peripheral portion of the base 1, locking screw insert holes
1b are formed (in this embodiment, two locations) so as to receive
respective locking screws (not shown) in a direction downward from the
first surface of the base 1. The locking screws are used to removably
mount the LED unit 10 to a housing 11 (see FIG. 9) of a lighting fixture
12 (see FIG. 9).

[0040] Here, in the LED unit 10 of this embodiment, the base 1 has a
circular shape. However, the shape of the LED unit may have a variety of
shapes, for example, a polygonal shape or an elliptical shape, without
being limited to the circular shape.

[0041] The light-emitting device 3 includes a light-emitting unit 3a
having LED chips, and a mounting board 3b on which the light-emitting
unit 3a is mounted. Here, the LED chips are connected to each other in
series. However, the LED chips may be connected to each other in parallel
or in series and parallel.

[0042] The light-emitting unit 3a includes LED chips (not shown), a
peripheral wall 3e that surrounds the LED chips and reflects light
emitted from the LED chips, and an envelope part 3d that covers the LED
chips placed inside the peripheral wall 3e. Further, in the
light-emitting unit 3a, the LED chips are blue LED chips that emit blue
light and a fluorescent material including a yellow fluorescent material
that can be excited by the blue light emitted from the blue LED chips to
emit yellow light of broad spectrum is mixed in a light transmissive
envelope material (for example, silicone resin, epoxy resin, glass, etc.)
of the envelope part 3d, so that the light-emitting unit 3a serves as a
white LED that emits white light. Further, the color of the fluorescent
material of the light-emitting unit 3a may be, for example, red or green
without being limited to the yellow. Further, the light-emitting unit 3a
may become the white LED by combining UV (ultra violet) and NUV (near
ultra violet) LED chips, a red fluorescent material, a green fluorescent
material and a blue fluorescent material.

[0043] Further, the light-emitting unit 3a may become the white LED by
combining red LED chips, green LED chips and blue LED chips.

[0044] The mounting board 3b is made using, for example, a metal base
printed wiring board, and a pair of terminals 3c is formed on the board
3b. The terminals 3c are electrically connected to the light-emitting
unit 3a and are formed by respective conductive patterns. Although the
mounting board 3b uses the metal based printed wiring board in this
embodiment, the mounting board 3b may use, for example, a ceramic board
or a glass epoxy board without being limited to the metal base printed
wiring board. Further, the wires 4 are electrically connected to the
respective terminals 3c via connection parts (not shown) formed by
solder. Here, one wire 4 is connected to one terminal 3c (the left-hand
terminal 3c in FIG. 1) that is connected to the positive pole of the
light-emitting unit 3a, while the other wire 4 is connected to the other
terminal 3c (the right-hand terminal 3c in FIG. 1) that is connected to
the negative pole of the light-emitting unit 3a. Further, in order to
prevent a connection error of the wires 4, the mounting board 3b is
marked with polarity symbols "+", "-" at predetermined locations around
the respective terminals 3c. Further, a reflective layer (not shown) made
of a white resist layer is formed on a first surface of the mounting
board 3b in such a way that the layer covers the mounting board 3b except
for portions corresponding to the light-emitting unit 3a and the
terminals 3c, and thus light emitted from the light-emitting unit 3a can
be prevented from being absorbed by the mounting board 3b.

[0045] Further, the heat-dissipating sheet 9 is placed between a second
surface of the mounting board 3b and the support block 1f protruding from
the first surface of the base 1. Accordingly, the light-emitting device 3
can efficiently dissipate heat to the base 1 through the heat-dissipating
sheet 9. Further, in the LED unit 10 of this embodiment, the base 1 is
made of aluminum that has higher heat conductivity than that of resin, so
that heat generated from the light-emitting device 3 can be efficiently
dissipated to the housing 11 through the heat-dissipating sheet 9 and the
support block 1f of the base 1.

[0046] The heat-dissipating sheet 9 uses a silicone gel sheet formed of a
silicone resin including a gel-phase elastic polymer (elastomer). The
gel-phase elastic polymer is in a gel phase and is soft with a low
cross-link density and has elasticity. In this embodiment, the
heat-dissipating sheet 9 is formed using the silicone gel sheet, however,
the heat-dissipating sheet 9 may be formed using another material that
has both high electrical insulation property and high heat conductivity
and can be easily filled in slits 1g. Accordingly, without being limited
to the silicone gel, the material of the heat-dissipating sheet 9 may be
selected from soft elastic polymer materials (for example, an acrylic
resin material) that have high electrical insulation property and high
heat conductivity. Further, the heat-dissipating sheet 9 may be formed of
adhesive material to be used as an adhesive sheet.

[0047] On the first surface of the base 1, a circular depression 1e is
formed so as to receive some portions of the wires 4 electrically
connected to the light-emitting device 3.

[0048] At the central portion of the bottom surface of the depression 1e,
the support block 1f is provided to protrude toward the light-emitting
device 3 (protruding upward in FIG. 1). When viewed from the top, the
support block 1f has a square shape (a rectangular shape in this
embodiment). Here, the light-emitting device 3 is placed in such a way
that the heat dissipating sheet 9 is interposed between the
light-emitting device 3 and the upper surface 1fa of the support block
1f.

[0049] Further, the height of the support block 1f is determined such that
the sum of the height of the support block 1f and the thickness of the
heat-dissipating sheet 9 is greater than the depth of the depression 1e.
Accordingly, the support block 1f can suppress light reflected by the
light-emitting device 3 from being reflected or absorbed by the inner
surface of the depression 1e of the base 1.

[0050] Further, on the upper surface 1fa of the support block 1f, slits 1q
for receiving a portion of the soft heat-dissipating sheet 9 are formed
at predetermined locations (four locations in FIG. 1). Due to the slits
1q, during the process of assembling the LED unit 10, it is possible to
prevent the heat-dissipating sheet 9 interposed between the support block
1f and the light-emitting device 3 from transversely deviating from a
desired location before the light-emitting device 3 and the
light-emitting sheet 9 are held between the base 1 and the holder 2.

[0051] Specifically, the support block 1f is provided with the slits 1q on
peripheral portions of the upper surface 1fa and the heat-dissipating
sheet 9 is mounted on the upper surface 1fa, so that some portions of the
heat-dissipating sheet 9 can be inserted into the slits 1g. Here, the
portions of the heat-dissipating sheet 9 inserted into the slits 1q
function as anchors capable of preventing a positional deviation of the
heat-dissipating sheet 9 from a desired location. Accordingly, even when
vibration is applied to the LED unit 10 during the process of assembling
the LED unit 10 as will be described later herein with reference to FIGS.
5A, 5B, 8A and 8B, a positional deviation of the heat-dissipating sheet 9
from the support block 1f can be restricted by the portions of the
heat-dissipating sheet 9 inserted into the slits 1q.

[0052] Here, the shape, width and depth of the slits 1q formed in the
support block 1f may be appropriately determined according to the
thickness of the heat-dissipating sheet 9 and to the size and shape of
the light-emitting device 3. For example, when the thickness of the heat
dissipating sheet 9 is 1.0 mm, the width and depth of the slits 1q may be
set to a range of 0.3 to 0.5 mm. The size of the heat-dissipating sheet 9
is determined such that the sheet 9 can cover the slits 1q. Here, the
heat-dissipating sheet 9 having the above-mentioned size may be laid on
the upper surface 1fa. That is, the slits 1q are formed in the peripheral
portion of the upper surface 1fa on which the heat-dissipating sheet 9 is
to be placed.

[0053] Further, when viewing the support block 1f from the top, the slits
1q are formed on the upper surface 1fa of the rectangular support block
1f at peripheral portions corresponding to the four sides of area on
which the heat-dissipating sheet 9 is to be placed, so that it is easy to
determine whether the heat-dissipating sheet 9 deviates from a desired
location or not. When the heat-dissipating sheet 9 deviates from the
desired location during the process of assembling the LED unit 10, one or
more of the slits 1q are exposed outside the heat-dissipating sheet 9 so
that it is easy to determine the deviation of the heat-dissipating sheet
9.

[0054] The holder 2 includes a pressing plate part 2e that holds the
light-emitting device 3 between the holder 2 and the support block 1f,
and a peripheral wall 2f that extends from the edge of the pressing plate
part 2e toward the base 1. The pressing plate part 2e of the holder 2 is
a circular plate, with a window opening 2a formed in the central portion
thereof so as to expose the light-emitting unit 3a of the light-emitting
device 3.

[0055] Here, bosses 1r are formed to protrude from the bottom surface of
the depression 1e at locations opposed to each other in a width direction
of the support block 1f. The bosses 1r are provided with respective screw
holes 1d into which locking screws 23d used for mounting the holder 2 to
the base 1 are tightened. Accordingly, when compared to a case in which
the bosses 1r are formed at locations opposed to each other in a
lengthwise direction of the support block 1f, it is possible to reduce
the size of the pressing plate part 2e of the holder 2 in the LED unit
10.

[0056] Further, in the peripheral portion of the pressing plate part 2e of
the holder 2, openings 2b are formed in such a way that they communicate
with the window opening 2a. Here, the openings 2b can prevent the wires 4
electrically connected to the terminals 3c of the light-emitting device 3
from interfering with the holder 2.

[0057] Further, screw insert holes 2d are formed at the peripheral portion
of the pressing plate part 2e of the holder 2 correspondingly to the
respective screw holes 1d of the base 1, so that the locking screws 23d
can be inserted into the respective screw insert holes 2d from a front
surface side (the upper surface side in FIG. 1) of the pressing plate
part 2e of the holder 2. Here, when the holder 2 is mounted to the base
1, the light-emitting unit 3a of the light-emitting device 3 is exposed
through the window opening 2a of the holder 2 and the light-emitting
device 3 is held between the base 1 and the holder 2. Further, the
locking screws 23d are inserted into the respective screw insert holes 2d
in a downward direction from the upper surface side of the pressing plate
part 2e of the holder 2 to be tightened to the respective screw holes 1d
of the base 1, thereby mounting the holder 2 to the base 1. Here, the
heat-dissipating sheet 9 is interposed between the light-emitting device
3 and the base 1.

[0058] Accordingly, when the locking screws 23d are tightened to the
respective screw holes 1d in the LED unit 10 of this embodiment, stress
that may be applied to the light-emitting device 3 is lowered because the
stress can be absorbed by the heat-dissipating sheet 9, so that it is
possible to prevent undesired stress from being applied to the
light-emitting device 3.

[0059] In the LED unit 10 of this embodiment, the pressing plate part 2e
of the holder 2 has a circular shape, however, the shape is not limited
thereto and may be changed into other shapes, for example, a polygonal
shape or an elliptical shape.

[0060] Further, in the peripheral portion of the base 1, a wire lead mouth
1c is provided to guide the wires 4 that are electrically connected to
the light-emitting device 3 to the outside of the LED unit 10.

[0061] The wire lead mouth 1c is a notch that is formed in the peripheral
portion of the base 1 and allows a user to change the direction in which
the wires 4 are guided to the outside of the LED unit 10.

[0062] Specifically, the wire lead mouth 1c is formed by opening a second
surface of the base 1 (the lower surface in FIG. 2), the side surface and
the first surface of the base 1 in the peripheral portion of the base 1.
That is, due to the wire lead mouth 1c, the direction in which the pair
of wires 4 is guided to the outside of the LED unit 10 can be changed
between a direction toward the second surface of the base 1 and a
sideward direction of the base 1 (see the circular arc-shaped arrow in
FIG. 2). Further, the wire lead mouth 1c is configured such that when the
pair of wires 4 is led through the wire lead mouth 1c to a direction
perpendicular to the second surface of the base 1, the wires 4 can be
placed inside the outer periphery of the base 1.

[0063] Accordingly, in the LED unit 10 of this embodiment, it is possible
to guide the wires 4 to the direction toward the second surface of the
base 1 and the side direction of the base 1 through the wire lead mouth
1c. That is, compared to the conventional LED unit shown in FIGS. 16A and
16B, in the LED unit 10 of this embodiment, it is possible to increase
the degree of freedom of relative positional relationship between the LED
unit 10 and a power unit 15 (see FIG. 9) that supplies electricity to the
LED unit 10. Because the degree of freedom of relative positional
relationship between the LED unit 10 and the power unit 15 can be
increased, the LED unit 10 may be easily mounted to various housings 11
having different shapes. Further, as described above, the wire lead mouth
1c is configured in such a way that when the wires 4 are guided through
the wire lead mouth 1c to the direction perpendicular to the second
surface of the base 1, the wires 4 can be placed inside the outer
circumference of the base 1. Accordingly, when the housing 11 is a
cylindrical housing as an example, it is possible to set the minimum
diameter of the housing 11 to about the size of the base 1, thereby to
make the lighting fixture 12 compact.

[0064] However, in the depression 1e of the base 1, ribs 1ha and 1hb
protrude from the inner bottom surface of the depression 1e at locations
around the wire lead mouth 1c (the ribs protrude downwards in FIG. 2).
The ribs 1ha and 1hb hold the respective wires 4 against the inner
circumferential surface of the depression 1e (see FIG. 6A). Specifically,
on the inner bottom surface of the depression 1e of the base 1 at
locations around the wire lead mouth 1c, the first rib 1ha protrudes so
as to hold the first wire 4 against the inner circumferential surface of
the depression 1e, and the second rib 1hb protrudes so as to hold the
second wire 4 against the inner circumferential surface of the depression
1e. Further, on the inner bottom surface of the depression 1e of the base
1, a rib 1hc protrudes at a predetermined location between two ribs 1hd
that protrude from the inner circumferential surface of the depression 1e
at borders with the inside surfaces 1g of the wire lead mouth 1c, so that
the rib 1hc holds the wires 4 (see FIG. 7A). Here, the rib 1hc is
integrated with the boss 1r. Further, the ribs 1ha and 1hb are connected
to each other by a connecting arm the that protrudes from the inner
bottom surface of the depression 1e of the base 1.

[0065] Accordingly, in the LED unit 10 of this embodiment, the wires 4
electrically connected to the light-emitting device 3 can be stably held
in the base 1 without being tensioned with no additional elements. That
is, the LED unit 10 of this embodiment does not need any additional
element for reducing the tension applied to the wires 4 so that the LED
unit 10 can easily reduce the tension of the wires 4 at low cost.
Further, because this LED unit 10 can reduce the tension applied to the
wires 4 as described above, it is possible to prevent any disconnection
that may be caused by stress applied to the connection parts (not shown)
between the wires 4 and the terminals 3c of the light-emitting device 3.

[0066] Further, on a side surface of the holder 2 of the LED unit 10, a
holding part 2c is formed at a location corresponding to the wire lead
mouth 1c of the base 1 so as to hold the wires 4 guided through the wire
lead mouth 1c in cooperation with the base 1. That is, in the LED unit 10
of this embodiment, the wires 4 electrically connected to the
light-emitting device 3 can be held in the base 1 and between the base 1
and the holding part 2c.

[0067] Further, as shown in FIG. 2, the base 1 is provided with a chamfer
1k between the inside surface 1g of the wire lead mouth 1c formed in the
base 1 and the inner bottom surface of the depression 1e of the base 1.
Because the chamfer 1k is formed in the base 1 of the LED unit 10, it is
possible to reduce the stress that may be applied to the wires 4 when the
wires 4 are biased toward the second surface of the base 1. Further, when
the wires 4 are biased toward the second surface of the base 1 in the LED
unit 10, the stress that may be applied to the wires 4 can be reduced as
described above, so that it is possible to prevent the wires 4 from being
disconnected by the stress. Further, in this embodiment, the chamfer 1k
is configured as a C-chamfer, however, it should be understood that the
chamfer may be configured as, for example, an R-chamfer without being
limited to the C-shaped chamfer.

[0068] Further, the wire lead mouth 1c may be formed by opening the side
surface and the first surface (the upper surface in FIG. 2) in the
peripheral portion of the base 1 in addition to the second surface (the
lower surface in FIG. 2) of the peripheral portion of the base 1.
Further, in the peripheral portion of the cover pressing member 21, it is
preferred that an open portion corresponding to the wire lead mouth 1c be
formed by opening a second surface, the side surface and a first surface
of the cover pressing member 21 even though it is not shown in the
drawings. Accordingly, the wire lead mouth 1c allows the direction in
which the wires 4 are led to the outside of the LED unit 10 to be changed
between the direction toward the second surface of the base 1 and the
direction toward the first surface of the base 1. Therefore, the degree
of freedom of relative positional relationship between the LED unit 10
and the power unit 15 can be increased, and the LED unit 10 can be easily
mounted to various housings 11 having different shapes.

[0069] The cover 20 is made of a light-transmissive material (for example,
a silicone resin, an acrylic resin, glass, etc.). Further, the cover 20
includes a cylindrical cover body 20a that is placed inside the periphery
of the base 1 and has a bottom capable of covering the light-emitting
device 3, and a rim 20b that extends outward from the edge of the cover
body 20a and is used to mount the cover 20 to the base 1. The cover body
20a includes a circular light-transmitting part 20h that is disposed at a
distant from the base 1 and transmits light emitted from the
light-emitting device 3, and a cylindrical part 20j that extends from the
light-transmitting part 20h toward the base 1. Here, a lens may be
provided in the light-transmitting part 20h. Further, the shape of the
cover body 20a may be configured to have, for example, a dome-shape
without being limited to the cylindrical shape.

[0070] Further, a decorative cover 40 is placed between a surface (a lower
surface in FIG. 1) of the cover 20 directed toward the base 1 and the
upper surface of the pressing plate part 2e of the holder 2. The
decorative cover 40 has a ring shape (for example, a circular ring shape)
and covers the locking screws 23d passing through the respective screw
insert holes 2d of the holder 2 and the wires 4 and 4 exposed through the
openings 2b of the holder 2.

[0071] The decorative cover 40 is made of a light-shielding material (for
example, a white opaque resin, etc.) and is placed inside the cover body
20a of the cover 20. The decorative cover 40 has at a central portion
thereof a window opening 40b for exposing the light-emitting unit 3a of
the light-emitting device 3. An inner peripheral surface 40c of the
window opening 40b is appropriately inclined to reflect the light emitted
from the light-emitting unit 3a to obtain a desired light distribution.

[0072] Accordingly, because the decorative cover 40 that has the inner
peripheral surface 40c of the window opening 40b and an outer peripheral
surface 40d extending outward from the inner peripheral surface 40c is
placed on the upper surface of the pressing plate part 2e of the holder 2
in the LED unit 10 of this embodiment, it is possible to prevent the
locking screws 23d and the wires 4 from being viewed from the outside
through the cover 20 and, thus, a good appearance of the LED unit 10 can
be realized.

[0073] Further, in the peripheral portion of the rim 20b of the cover 20,
an annular protruding part 20e (see FIG. 2) protrudes toward the base 1.
Here, the groove 1t is formed in the first surface of the base 1 at a
location corresponding to the protruding part 20e of the cover 20 so as
to receive the protruding part 20e therein. A sealing material (for
example, a silicone resin) is filled in the groove 1t so as to form a
seal 5. Accordingly, in the LED unit 10 of this embodiment, the
protruding part 20e of the cover 20 is inserted into the groove 1t of the
base 1 so that the base 1 and the cover 20 are sealed through the seal 5,
thereby preventing the moisture or impurities from being introduced into
the LED unit 10.

[0074] Specifically, in the LED unit 10 of this embodiment, the acrylic
cover 20 that has a function as a lens transmitting the light emitted
from the light-emitting device 3 is mounted to the base 1 by using the
cover pressing member 21. Here, the protruding part 20e of the cover 20
is inserted into the groove 1t. Further, the base 1 used in the LED unit
10 of this embodiment has the annular groove 1t that is formed on the
first surface of the base 1 as shown in FIGS. 3A and 35 and receives the
seal 5 therein. Here, the groove 1t is configured in such a way that
inward protrusions 1tb are protruded radially inwardly from the outer
circumferential surface of the groove 1t and, thus, the distance between
the protruding part 20e (see the two-dot chain line in FIGS. 3A and 3B)
and the groove 1t in the width direction of the groove 1t is shorter in
the section of the groove 1t having the inward protrusions 1tb than the
other section of the groove it. In this embodiment, the inward
protrusions 1tb are the arc-shaped protrusions that are protruded
radially inwardly from the outer circumferential surface of the groove
1t, however, the shape of the inward protrusions 1tb may have a variety
of shapes without being limited to the arc shape if the inward
protrusions 1tb are protruded radially inwardly from the outer
circumferential surface of the groove 1t.

[0075] Further, the inward protrusions 1tb are disposed at two locations
of the outer circumferential surface of the groove 1t in this embodiment,
they may be disposed at an inner circumferential surface of the groove
1t, and the number of protrusions is not limited to two.

[0076] In other words, the inward protrusions 1tb of the groove 1t form a
specified structure in which the distance between the protruding part 20e
and the groove 1t in the width direction of the groove 1t is shorter in
the section of the groove 1t having the inward protrusions 1tb than the
other section of the groove 1t, which makes the seal 5 have thinner parts
5a (see FIG. 3B). Here, the hardening time of the sealing material that
forms the seal 5 depends upon the amount of the sealing material.
Therefore, the hardening time of the sealing material is shorter in the
thinner parts 5a compared to thicker parts 5b, and the hardening of the
material of the seal 5 is started at the thinner parts 5a of the seal 5,
so that the thinner parts 5a can be more quickly hardened than the
thicker parts 5b. Accordingly, it is possible to prevent the cover 20
from undesirably deviating from a desired location by vibration applied
thereto during the process of hardening the material of the seal 5.

[0077] Further, even when a torque is applied to the cover 20 after the
sealing material has been hardened, the inward protrusions 1tb that
inwardly protrude from the outer circumferential surface of the groove 1t
function to stop a rotation of the thicker parts 5b of the seal 5,
thereby restricting a rotation of the cover 20. When compared to an LED
unit in which the seal 5 is inserted into a groove having a simple
annular shape without the protrusions, the LED unit 10 of this embodiment
can increase the adherence of the seal 5 relative to the cover 20 and the
base 1 against a torque applied to the cover 20.

[0078] That is, during the process of assembling the LED unit 10 of this
embodiment, the seal 5 is inserted into the groove 1t and, thereafter,
the protruding part 20e of the cover 20 is inserted into the groove 1t,
so that the base 1 and the cover 20 are sealed through the seal 5,
thereby preventing moisture or impurities being introduced into the LED
unit 10. Further, the LED unit 10 is configured in such a way that the
distance between the protruding part 20e and the groove 1t in the width
direction of the groove 1t is shorter in a section of the groove 1t than
the other sections, thereby reducing the hardening time of the sealing
material and increasing the adherence of the hardened sealing material
relative to the cover 20 and the base 1 against a torque applied to the
cover 20.

[0079] The material of the seal 5 of this embodiment uses a silicone
resin. However, the seal 5 may use another resin material (for example,
epoxy resin, urethane resin, etc.).

[0080] The cover pressing member 21 is made of a light-shielding material
(for example, metal, such as aluminum, a white opaque resin, etc.) and is
configured as a flat ring-shaped structure (a circular ring-shaped
structure in the embodiment) such that the cover pressing member 21 does
not disturb the light which is emitted from the light-emitting device 3
and transmitted through the cover body 20a of the cover 20. Here, the rim
20b of the cover 20 is held between the cover pressing member 21 and the
base 1.

[0081] Further, on a surface of the cover pressing member 21 that is
directed toward the base 1, a channel 21a is formed in the peripheral
portion of the cover pressing member 21 at a location corresponding to
the wire lead mouth 1c of the base 1, as shown in FIG. 5B, so that when
the sealing material of the seal 5 filled in the groove 1t of the base 1
overflows during a process of assembling the LED unit 10, the channel 21a
can collect the overflowing sealing material. Here, in the outer
circumferential portion of the rim 20b of the cover 20, a guide notch 20f
is formed at a location corresponding to the channel 21a of the cover
pressing member 21, as shown in FIG. 5A. The guide notch 20f guides the
overflowing material of the seal 5 to the channel 21a of the cover
pressing member 21.

[0082] Further, cylindrical bosses 21c (four bosses in this embodiment)
are formed on the first surface (a lower surface in FIG. 1) of the cover
pressing member 21 in such a way that the bosses 21c protrude toward the
base 1 (see FIG. 5B). Here, semicircular cutouts 20d are formed in the
outer edge of the rim 20b of the cover 20 at locations corresponding to
the bosses 21c of the cover pressing member 21 so that the bosses 21c can
pass therethrough. Further, in the peripheral portion of the base 1,
through holes 1a are formed at locations corresponding to the respective
bosses 21c of the cover pressing member 21 so as to receive the bosses
21c therein. Here, when the cover 20 is mounted to the base 1, the bosses
21c of the cover pressing member 21 are inserted into the respective
through holes 1a of the base 1 and, thereafter, the leading ends of the
bosses 21c are irradiated by, for example, laser beams from the side of
the second surface (the lower surface in FIG. 1) of the base 1, thereby
being plastically deformed so that the diameters of the ends become
greater than those of the through holes 1a of the base 1 and,
accordingly, the cover 20 can be attached to the base 1. In other words,
the shape of the bosses 21c is changed to a mushroom shape. Here, on the
second surface of the base 1, depressions 1j are formed at locations
corresponding to the respective through holes 1a in such a way that the
depressions 1j communicate with the respective through holes 1a and
receive the heads of the mushroom-shaped bosses 21c. The depth of the
depressions 1j is determined in such a way that the heads of the
mushroom-shaped bosses 21c do not protrude from a plane including the
second surface of the base 1.

[0083] In the LED unit 10 of this embodiment, the rim 20b of the cover 20
is held between the base 1 and the cover pressing member 21 so that it is
possible to prevent excessive stress from being applied to the cover 20.
Further, in the LED unit 10, the cover pressing member 21 is mounted to
the base 1 without using locking screws so that the LED unit 10 can be
free from a problem caused by the screws that may be loosened. Further,
in the LED unit 10, the cover pressing member 21 has a flat ring shape so
that when the LED unit 10 mounted to the housing 11 is turned on, the
desired distribution and uniformity of light transmitted through the
cover body 20a of the cover 20 are not reduced. Further, the method of
mounting the cover 20 to the base 1 may be accomplished by using, for
example, locking screws without being limited to the above.

[0084] Further, on the edge of the cover pressing member 21, semicircular
cutouts 21b are formed at locations corresponding to the respective
locking screw insert holes 1b of the base 1 so as to allow locking screws
(not shown) to pass through the cover pressing member 21 from the side of
the second surface (the upper surface in FIG. 1) of the cover pressing
member 21. Further, on the edge of the rim 20b of the cover 20,
semicircular cutouts 20c are formed at locations corresponding both to
the respective locking screw insert holes 1b of the base 1 and to the
respective cutouts 21b of the cover pressing member 21 so as to allow the
locking screws to pass through the cover 20 from the side of the cover
pressing member 21. Accordingly, because the cutouts 21b are formed on
the edge of the cover pressing member 21 and the cutouts 20c are formed
on the edge of the rim 20b of the cover 20 in the LED unit 10 of this
embodiment, it is possible to removably mount the base 1 of the LED unit
10 to the housing 11 of the lighting fixture 12 from the side of the
cover 20.

[0085] Further, the wires 4 are provided with a connector 4a at the ends
thereof led through the wire lead mouth 1c of the base 1. This connector
4a may be detachably connected to a connector 14 that is provided at the
end of a wire 13 electrically connected to the power unit 15, as shown in
FIG. 9.

[0086] Accordingly, in the LED unit 10 of this embodiment, because the
connector 4a is provided at the ends of the wires 4 so as to be
detachably connected to the connector 14 of the power unit 15, which
makes connecting/disconnection from the LED unit 10 easy. Further, in the
LED unit 10, the connector 4a is provided at the ends of the wires 4 and
the base 1 can be removably mounted to the housing 11 of the lighting
fixture 12 from the side of the cover 20, so that a user can easily
replace the LED unit 10 with a new one.

[0087] Hereinbelow, the process of assembling the LED unit 10 will be
described with reference to FIGS. 6A to 8B.

[0088] First, on the upper surface 1fa of the rectangular support block 1f
provided on the first surface of the base 1 shown in FIG. 6A, the
rectangular heat-dissipating sheet 9 having a size larger than that of
the upper surface 1fa is laid (see FIG. 68). Here, by laying the
heat-dissipating sheet 9 on the upper surface 1fa of the support block
1f, a portion of the heat-dissipating sheet 9 is inserted into the slits
1q of the upper surface 1fa.

[0090] Consequently, the wires 4 are held by the inner circumferential
surface of the depression 1e of the base 1 and the ribs 1ha and 1hb, and
the wires flare electrically connected to the terminals 3c of the
mounting board 3b (see FIG. 7A).

[0091] Thereafter, the light-emitting device 3 is covered with the holder
2 and the holder 2 is fixed to the base 1 by using the locking screws 23d
(see FIG. 7B).

[0092] On the holder 2, the decorative cover 40 is placed to surround the
light-emitting unit 3a of the light-emitting device 3 (see FIG. 70).

[0093] Thereafter, the material of the seal 5 is applied to the groove 1t
of the base 1 (see FIG. 7C), and the protruding part 20e of the cover 20
is inserted into the groove 1t in a state that lugs 40a protruding from
the peripheral portion of the decorative cover 40 are aligned with
respective recessed parts 20g formed in the inner circumferential surface
of the cover 20. Accordingly, the cover 20 is placed on the base 1 (see
FIG. 8A).

[0094] Here, unlike the embodiment in which the cover 20 is placed on the
base 1 after the decorative cover 40 has been placed on the base 1 to
surround the light-emitting unit 3a of the light-emitting device 3 as
shown in FIG. 7C, the cover 20 may be placed on the base 1 after the
decorative cover 40 has been temporarily maintained in the cover 20 by
inserting the lugs 40a of the decorative cover 40 into the respective
recessed parts 20g of the cover 20.

[0095] Finally, the bosses 21c of the cover pressing member 21 are
inserted into the respective through holes 1a of the base 1 and,
thereafter, the leading ends of the bosses 21c are irradiated by, for
example, laser beams from the side of the second surface of the base 1 to
be plastically deformed, thereby finishing the assembly of the LED unit
10 (see FIG. 8B).

[0096] A lighting fixture 12 having the LED unit 10 that has been
assembled by the above-mentioned process will be described with reference
to FIGS. 9 to 14.

[0097] The lighting fixture 12 includes an LED unit 10 and a metal housing
11 to which the LED unit 10 can be removably mounted. In the lighting
fixture 12, the housing 11 is a metal housing so that unlike a resin
housing, heat generated from the light-emitting device 3 of the LED unit
10 can be efficiently dissipated to the surroundings via the
heat-dissipating sheet 9, the base 1 and the housing 11. Further, in the
embodiment, the material of the housing 11 is aluminum, however, the
material of housing 11 may use another metal without being limited to
aluminum. Further, the material of the housing 11 may be other material
than metal.

[0098] The housing 11 is configured so that the LED unit 10 can be easily
removably mounted to the housing 11. Specifically, the housing 11 is
provided with screw holes (not shown) at locations corresponding to the
respective locking screw insert holes 1b of the base 1 so that locking
screws can be tightened to the screw holes.

[0099] The lighting fixture 12 having the construction shown in FIG. 9 is,
for example, a downlight that is embedded in a ceiling member 17. The
housing 11 of this lighting fixture 12 includes a cylindrical housing
body 11a that has a bottom for holding an LED unit 10, and a flange part
11b that extends outward from the outer edge of the housing body 11a.
Further, the housing 11 is installed in an embedding hole 17a that is
formed in the ceiling member 17, so that the flange part 11b of the
housing 11 can come into contact with the peripheral portion of the
embedding hole 17a on the surface of the ceiling member 17 and can be
mounted to the ceiling member 17.

[0100] A chamber 11e is provided on the bottom 11c of the housing 11 so as
to hold the power unit 15 therein. Here, the power unit 15 installed in
the housing 11 is spaced apart from the housing 11 so that the lighting
fixture 12 of this embodiment can prevent heat of the power unit 15 from
being transferred to the LED unit 10 via the housing 11.

[0101] Further, a lead hole (not shown) is formed through the bottom 11c
of the housing 11 so as to lead the wires 4 and the connector 4a led from
the LED unit 10 into the chamber 11e.

[0102] Further, the lighting fixture 12 having the construction shown in
FIG. 10 is, for example, a spotlight of which the housing 11 is held by a
housing holder 19 that is mounted to the ceiling member 17. The housing
11 of this lighting fixture 12 is a box-shaped housing. Here, the power
unit 15 installed inside housing 11 is spaced apart from the housing 11.

[0103] In this lighting fixture 12, a lead hole (not shown) is formed
through the bottom 11c of the housing 11 so as to lead the wires 4 and
the connector 4a led from the LED unit 10 into the housing 11. Further,
on the bottom 11c of the housing 11, a diffusing plate 22 is mounted to
cover the LED unit 10, the diffusing plate 22 serving to diffuse and
transmit light emitted from the cover 20 of the LED unit 10.

[0104] Further, the lighting fixture 12 having the construction shown in
FIG. 11 is, for example, a bracket light of which the housing 11 is
mounted to a wall 18. The housing 11 of this lighting fixture 12 is a
box-shaped housing in which the power unit 15 is installed to be spaced
apart from the housing 11. Further, in the housing 11, a diffusing plate
22 is mounted cover the LED unit 10, the diffusing plate 22 serving to
diffuse and transmit light emitted from the cover 20 of the LED unit 10.

[0105] In the LED units 10 installed in the lighting fixtures 12 shown in
FIGS. 9 to 11, the wires 4 are led to the side of second (the lower
surface in FIG. 2) of the base 1 through the wire lead mouth 1c of the
base 1, as shown in FIG. 2.

[0106] Further, the lighting fixture 12 having the construction shown in
FIG. 12 is, for example, a ceiling light in which the power unit 15 is
placed aside by the LED unit 10 and the housing 11 is mounted to the
ceiling member 17. Further, the lighting fixture 12 having the
construction shown in FIG. 13 is, for example, a pendant light of which
the housing 11 is suspended from the a suspending unit 16 that is mounted
to the ceiling member 17 and suspends the housing 11. Further, the
lighting fixture 12 having the construction shown in FIG. 14 is, for
example, a porch light in which the power unit 15 is placed below the LED
unit 10 and the housing 11 is a longitudinal housing that is mounted to a
wall 18. Further, each of the lighting fixtures 12 of FIGS. 12 to 14 has
a diffusing plate 22 that diffuses and transmits light emitted from the
cover 20 of the LED unit 10.

[0107] In the LED units 10 installed in the lighting fixtures 12 shown in
FIGS. 12 to 14, the wires 4 are led to a lateral side (the left side in
FIG. 2) of the base 1 through the wire lead mouth 1c of the base 1, as
shown in FIG. 2. In these embodiments, the lighting fixtures 12 may be
lighting fixtures that have LED units 10 capable of being mounted to a
variety of housings 11.

[0108] While the invention has been shown and described with respect to
the preferred embodiments, it will be understood by those skilled in the
art that various changes and modifications may be made without departing
from the scope of the invention as defined in the following claims: